Obesity now affects an estimated 2.8 million children between the ages of 2 and 5 years, as the prevalence of obesity among preschool school age children has almost tripled from 5 percent of the population in 1971-1980 to 13.9 percent by 2004. Being obese at age 5 confers a 47 times greater risk of being overweight or obese at age 12. In fact being obese any time between 2 and 5 year increases the risk of remaining overweight or obese as an adult by four times the risk of nonobese preschoolers. Being obese as a preschooler also increases the risk of a number of serious health conditions, including a 2.6 times greater risk of developing type 2 diabetes by age 21 years. In fact, the obesity rate among preschoolers is thought to impose such a cumulative health risk across the life span that children born today, for the first time in history, are expected to have a shorter life expectancy than their parents by to 2 to 5 years. Early effective treatments for establish obesity during the preschool years have the potential to change the trajectory of obesity and related co-morbid health condition across the life-span by reducing obesity and changing the development of lifestyle habits of diet and exercise at a time when these are being formed. Yet research on interventions to reduce obesity in preschool children is severely limited and none exist that addresses established obesity in this age group. Therefore the current study has the potential to have a significant impact on public health by providing evidence-based treatment for obesity in preschoolers, a developmental period in which eating and activity patterns are being formed, that could significantly impact the trajectory of obesity thereby decreasing the population obesity rates and associated healthcare costs at across the life span. Fortunately, we are on our way to addressing the problem of obesity reduction in already obese preschoolers. We have developed and conducted a pilot randomized clinical trial of a treatment program aimed at reducing obesity in already obese preschool children. Our program (Learning about Activity and Understanding Nutrition for Child Health: LAUNCH) is tailored to the developmental stage of preschool children and produced promising preliminary results. In the proposed trial a 3 arm, randomized, parallel group design will test LAUNCH against 1) motivational interviewing (attention control;MI) and 2) standard of care (true standard of care control;STC) with 168 children ages 2 to 5 years who meet the criteria for obesity (>95th percentile for body mass index;BMI). Participants will be randomized to receive a 6 month intervention (LAUNCH, MI) or standard of care. The primary end-point will be change in BMI z-score at the end of treatment. We will also assess maintenance of treatment gains at 6 and 12 months after treatment, and changes in factors thought to be mechanisms for change in weight (food intake and activity level), changes in the obesiogenic environment (parent weight, food intake and activity, and changes in the home food environment) and factors that could be negatively impacted (parent and child eating and feeding interactions). PUBLIC HEALTH RELEVANCE: Obesity among preschool children is a significant health problem affecting approximately 2.8 million children ages 2 to 5 years. There are no treatment studies to reduce established obesity in this age group. Because obesity during the preschool years tracks into childhood and adulthood and increases the likelihood of disorders such as type 1 diabetes, effective treatments for preschoolers are critical in order to change the trajectory of obesity and co-morbidities throughout the life course. Without intervention it is speculated that obesity trends will continue to occur at younger ages, children will carry obesity related health risks for a greater portion of their lives, and, for the first time in history, children born today will have a shorter life expectancy than their parents.